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From: Bradley Morgan <brads@mainlining.org>
To: Andrew Morton <akpm@linux-foundation.org>,
	Vineet Gupta <vgupta@kernel.org>, Guo Ren <guoren@kernel.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>, Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	David Laight <david.laight.linux@gmail.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org,
	linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org,
	Bradley Morgan <brads@mainlining.org>
Subject: [PATCH v2 3/5] csky: Emulate two-byte cmpxchg
Date: Wed, 16 Sep 2026 20:02:13 +0000	[thread overview]
Message-ID: <20260916200215.21774-4-brads@mainlining.org> (raw)
In-Reply-To: <20260916200215.21774-1-brads@mainlining.org>

CSKY has no two-byte atomic compare and swap, so the __cmpxchg()
switches in cmpxchg.h let case 2 fall through to the undefined
__cmpxchg_called_with_bad_pointer(), failing at link time. Route case
2 through the new cmpxchg_emu_u16(), which now takes natural u16
arguments, so the (uintptr_t) casts on __old and __new become (u16)
casts in all three switch instances.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/csky/include/asm/cmpxchg.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..e53628268e8c 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -65,6 +65,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -98,6 +101,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -132,6 +138,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		RELEASE_FENCE					\
-- 
2.47.3


WARNING: multiple messages have this Message-ID (diff)
From: Bradley Morgan <brads@mainlining.org>
To: Andrew Morton <akpm@linux-foundation.org>,
	Vineet Gupta <vgupta@kernel.org>, Guo Ren <guoren@kernel.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>, Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	David Laight <david.laight.linux@gmail.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org,
	linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org,
	Bradley Morgan <brads@mainlining.org>
Subject: [PATCH v2 3/5] csky: Emulate two-byte cmpxchg
Date: Wed, 16 Sep 2026 20:02:13 +0000	[thread overview]
Message-ID: <20260916200215.21774-4-brads@mainlining.org> (raw)
In-Reply-To: <20260916200215.21774-1-brads@mainlining.org>

CSKY has no two-byte atomic compare and swap, so the __cmpxchg()
switches in cmpxchg.h let case 2 fall through to the undefined
__cmpxchg_called_with_bad_pointer(), failing at link time. Route case
2 through the new cmpxchg_emu_u16(), which now takes natural u16
arguments, so the (uintptr_t) casts on __old and __new become (u16)
casts in all three switch instances.

Signed-off-by: Bradley Morgan <brads@mainlining.org>
---
 arch/csky/include/asm/cmpxchg.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/csky/include/asm/cmpxchg.h b/arch/csky/include/asm/cmpxchg.h
index db6dda47184e..e53628268e8c 100644
--- a/arch/csky/include/asm/cmpxchg.h
+++ b/arch/csky/include/asm/cmpxchg.h
@@ -65,6 +65,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -98,6 +101,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		"1:	ldex.w		%0, (%3) \n"		\
@@ -132,6 +138,9 @@
 	case 1:							\
 		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u8((volatile u8 *)__ptr, (uintptr_t)__old, (uintptr_t)__new); \
 		break;						\
+	case 2:							\
+		__ret = (__typeof__(*(ptr)))cmpxchg_emu_u16((volatile u16 *)__ptr, (u16)__old, (u16)__new); \
+		break;						\
 	case 4:							\
 		asm volatile (					\
 		RELEASE_FENCE					\
-- 
2.47.3

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  parent reply	other threads:[~2026-09-16 20:02 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-16 20:02 [PATCH v2 0/5] Add two-byte cmpxchg emulation and wire it into the architectures Bradley Morgan
2026-09-16 20:02 ` Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 1/5] lib: Add two-byte cmpxchg emulation function Bradley Morgan
2026-09-16 20:02   ` Bradley Morgan
2026-09-16 20:17   ` Bradley Morgan
2026-09-16 20:17     ` Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 2/5] ARC: Emulate two-byte cmpxchg Bradley Morgan
2026-09-16 20:02   ` Bradley Morgan
2026-09-16 20:02 ` Bradley Morgan [this message]
2026-09-16 20:02   ` [PATCH v2 3/5] csky: " Bradley Morgan
2026-09-17  9:04   ` David Laight
2026-09-17  9:04     ` David Laight
2026-09-17 14:45     ` Bradley Morgan
2026-09-17 14:45       ` Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 4/5] sh: " Bradley Morgan
2026-09-16 20:02   ` Bradley Morgan
2026-09-16 20:02 ` [PATCH v2 5/5] xtensa: " Bradley Morgan
2026-09-16 20:02   ` Bradley Morgan
2026-09-17  1:32   ` Max Filippov
2026-09-17  1:32     ` Max Filippov

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